1. Field of the Invention
The present invention relates to a magnetic tape machine having an automatic cartridge loader for carrying a cartridge recording medium.
2. Description of the Related Art
In recent years, an increase in storage capacity has been desired in association with an improvement in computer performance. For example, in a magnetic tape machine, it is strongly desired to make use of the characteristics of a cartridge recording medium (which will be hereinafter referred to also as a cartridge) as an exchangeable medium and to continuously process a plurality of cartridges. This desire is due to the fact that the use of the plurality of cartridges allows not only an improvement in storage and process capacity, but also a reduction of operator interaction, thereby contributing to a reduction in running cost.
An example known as the magnetic tape machine capable of processing a plurality of cartridges is a magnetic tape machine including a magnetic tape unit for performing read and write of data on each cartridge, a cartridge storing member having a plurality of cells capable of storing the plurality of cartridges, and an automatic cartridge loader for carrying each cartridge between each cell of the cartridge storing member and the magnetic tape unit. The automatic cartridge loader has, for example, an accessor movable in a direction of arrangement of the cells of the cartridge storing member. In general, robot control inclusive of a servo technique for controlling a moving speed of the accessor is performed by firmware. The firmware herein means hardware having computer programs and data unchangeable in user environment. In moving the accessor by a distance from one of the cells to another, the firmware calculates digital data of a current value to be applied to a motor for driving the accessor, and a DA converter then converts this digital data (DAC value) into an analog current value to thereby drive the accessor. A moving path of the accessor is composed of an acceleration region, a constant-speed region, and a deceleration region, for example.
In the conventional magnetic tape machine, the firmware is constructed under the condition that mechanical friction due to movement of the accessor is a constant value. Accordingly, if the shape of parts such as a shaft changes because of dust sticking to the parts, wearing, etc. during the operation of the machine, the firmware cannot cope with this problem to possibly cause errors. Further, a troublesome work is required in assembling the machine so that a constant friction value can be obtained.